蛹虫草多糖的化学修饰及体外抗氧化能力

将醇沉法得到的粗多糖，经柱层析得多糖纯品。对多糖纯品进行硫酸化、羧甲基化、乙酰化化学修饰，用于体外抗氧化活性研究。纯化后的蛹虫草多糖可以被多种化学试剂修饰，其取代度大小的顺序是：羧甲基化＞乙酰化＞硫酸化；修饰后的多糖表现出不同程度的抗氧化活性，其中羧甲基化和硫酸化可以明显提高多糖的抗氧化能力，对烷基自由基清除率提高最大，分别达到95.19%和73.58%，其次是清除羟自由基和超氧阴离子自由基，乙酰化修饰后抗氧化能力有所下降。因此，采用合适的修饰方法，可以明显提高蛹虫草多糖的抗氧化活性。

Chemical Modification and in vitro Antioxidant Activity of Polysaccharides from Cordyceps militaris

Crude Cordyceps militaris polysaccharides obtained by ethanol precipitation were purified by sequential column chromatographies on DEAE-cellulose 52 and Sephadex G-100. Further, purified Cordyceps militaris polysaccharides were successfully modified by either sulfation, carboxymethylation or acetylation and their antioxidant activity and that of their modification products were comparatively assessed based on the ability to in vitro scavenge superoxide anion, hydroxyl and alkyl free radicals. Carboxymethylation showed the largest degree of substitution for Cordyceps militaris polysaccharides, followed by acetylation and sulfation. Three different modification products revealed different antioxidant activities. Sulfation and carboxymethylation could obviously increase the antioxidant activity of Cordyceps militaris polysaccharides and result in the highest increase of respectively 95.19% and 73.58% in the scavenging rate against alkyl radical, followed by hydroxyl and superoxide anion radicals. A decrease in the ability to scavenge superoxide anion, hydroxyl and alkyl free radical, however, was observed after acetylation. Therefore, the antioxidant activity of polysaccharides from Cordyceps militaris can be improved remarkably through appropriate chemical modifications.